1. Field of the Invention
This invention relates to a disk cartridge including a disk for recording and/or reproducing, and more particularly though not exclusively to a disk cartridge including a writable disk, such as an optical disk or the like.
2. Description of the Prior Art
A disk cartridge disclosed in a prior application, "Japanese Utility Model Registration Application No. 59-138278" filed by the applicant of the present application, will be discribed referring to FIGS. 1 and 2.
As illustrated in FIG. 1, a writable disk 1, one of the recording mediums, such as an optical disk or the like is rotatably accommodated in an almost square-shaped cartridge 4 made of synthetic resin, such as polycarbonate resin or the like and comprising an upper half 2 and a lower half 3.
Turn table insertion circular openings 5 are provided in the respective centers of the upper half 2 and lower half 3. Optical head insertion openings 6 are so provided as to extend from the center toward one of the four sides of the cartridge 4, and covered by a shutter 7 made of a metal plate, such as a stainless steel plate or the like and in the shape of almost the letter "U" in cross section. The upper half 2 and lower half 3 are combined in one with screws 8.
As the disk cartridge is horizontally inserted into a disk player in direction of arrow a from the side near the optical head insertion openings, a projection 9 disposed within the disk player is inserted into a side groove 10 provided along one side 4a of the cartridge 4 in direction of arrow b. Then, a first rack 11 is slidingly moved in the direction of arrow b from the returned position indicated in chain-dotted lines to the advanced position indicated in solid lines in FIG. 2 against the force of a return spring, so that the shutter 7 is moved in direction of arrow c from the closed position indicated in chain-dotted lines to the opened position indicated in solid lines along another side 4b perpendicular to the side 4a of the cartridge 4 so as to open the optical head insertion openings 6.
As the disk cartridge is horizontally ejected from the disk player in direction of arrow d so as to separate the projection 9 from the first rack 11 in direction of arrow e, the first rack 11 is moved in direction of arrow e to the returned position indicated in chain-dotted lines due to the force of the return spring and simultaneously, the shutter 7 is moved in direction of arrow f to the closed position indicated in chain-dotted lines.
As illustrated in FIG. 2, a second rack 12 is so provided as to be slidingly movable in the directions of arrows c and f along the side 4b of the cartridge 4 and linked to the first rack 11 by a transmission mechanism 16 comprising two pinions 13, 15 and one intermediate gear 14, all of which are rotatably mounted in the cartridge 4. A torsion spring 19 used as a return spring is attached to the intermediate gear 14, so that the racks 11 and 12 are urged in the respective directions of arrows e and f by the force of the return spring 19. Thus, the second rack 12 is slidingly moved in the direction of arrow c along the guide shaft 17, as the first rack 11 is moved by the projection 9 in the direction of arrow b against the force of the return spring 19.
As the shutter 7 in the prior art covers only the optical head insertion openings 6 of the cartridge 4, the turn table insertion openings 5 of the cartridge 4 are always left opened, so that dust or the like easily enters in the cartridge through the turn table insertion openings 5 and adheres to the surface of the disk, and it causes a serious problem that recording and/or reproducing of the disk 1 are made incomplete due to the so-called dropout.
In the disk cartridge of this sort, the width l.sub.2 of the optical head insertion opening 6 is generally smaller than the width (the diameter) l.sub.1 of the turn table insertion opening 5, so that the width .sub.3 of the shutter 7 for covering only the optical head insertion opening 6, is made so small as to become the width l.sub.2 of the optical head insertion opening 6, and the stroke l.sub.4 of the shutter is also made small. Thus, the stroke l.sub.4 necessary for the shutter 7 to close and open the optical head insertion opening 6 is obtained, even when the stroke l.sub.5 of the first rack 11 is not magnified by the transmission mechanism 16.
Therefore, if it is intended that the shutter 7 is extended so that the turn table insertion openings 5 may be covered by the shutter 7 together with the optical head insertion openings 6, in order to prevent dust or the like from externing in the cartridge 4 through the turn table insertion openings 5, it becomes necessary to make the width l.sub.3 of the shutter 7 so large as to become the width l.sub.1 of the turn table insertion opening 5 and as an inevitable consequence, the stroke l.sub.4 of the shutter 7 must be also made larger.
In the prior art, the transmission mechanism 16 connecting the first rack 11 with the second rack 12, however, comprises two pinions 13, 15 and one gear 14 and as the result, the stroke of the second rack 12 is always the same as the stroke l.sub.5 of the first rack 11, so that the stroke l.sub.4 of the shutter is not made large with the transmission mechanism 16 disclosed in the prior art.
Of course, the stroke l.sub.4 of the shutter 7 in the prior art can be made larger, when the stroke l.sub.5 of the first rack 11 is made large and further, the size of the cartridge 4 is made large so as to make the pinions 13, 15 and gear 14 large, but the stroke l.sub.5 of the first rack 11 defined by the projection 9 and size of the cartridge 4 are dependent on the disk player, so that it is impossible to make the stroke l.sub.4 of the shutter 7 larger through the means above-mentioned.